path: root/drivers/pci/vgaarb.c

// SPDX-License-Identifier: MIT
/*
 * vgaarb.c: Implements VGA arbitration. For details refer to
 * Documentation/gpu/vgaarbiter.rst
 *
 * (C) Copyright 2005 Benjamin Herrenschmidt <benh@kernel.crashing.org>
 * (C) Copyright 2007 Paulo R. Zanoni <przanoni@gmail.com>
 * (C) Copyright 2007, 2009 Tiago Vignatti <vignatti@freedesktop.org>
 */

#define pr_fmt(fmt) "vgaarb: " fmt

#define vgaarb_dbg(dev, fmt, arg...)	dev_dbg(dev, "vgaarb: " fmt, ##arg)
#define vgaarb_info(dev, fmt, arg...)	dev_info(dev, "vgaarb: " fmt, ##arg)
#define vgaarb_err(dev, fmt, arg...)	dev_err(dev, "vgaarb: " fmt, ##arg)

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/pci.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/sched/signal.h>
#include <linux/wait.h>
#include <linux/spinlock.h>
#include <linux/poll.h>
#include <linux/miscdevice.h>
#include <linux/slab.h>
#include <linux/screen_info.h>
#include <linux/vt.h>
#include <linux/console.h>
#include <linux/acpi.h>
#include <linux/uaccess.h>
#include <linux/vgaarb.h>

static void vga_arbiter_notify_clients(void);

/*
 * We keep a list of all VGA devices in the system to speed
 * up the various operations of the arbiter
 */
struct vga_device {
	struct list_head list;
	struct pci_dev *pdev;
	unsigned int decodes;		/* what it decodes */
	unsigned int owns;		/* what it owns */
	unsigned int locks;		/* what it locks */
	unsigned int io_lock_cnt;	/* legacy IO lock count */
	unsigned int mem_lock_cnt;	/* legacy MEM lock count */
	unsigned int io_norm_cnt;	/* normal IO count */
	unsigned int mem_norm_cnt;	/* normal MEM count */
	bool bridge_has_one_vga;
	bool is_firmware_default;	/* device selected by firmware */
	unsigned int (*set_decode)(struct pci_dev *pdev, bool decode);
};

static LIST_HEAD(vga_list);
static int vga_count, vga_decode_count;
static bool vga_arbiter_used;
static DEFINE_SPINLOCK(vga_lock);
static DECLARE_WAIT_QUEUE_HEAD(vga_wait_queue);

static const char *vga_iostate_to_str(unsigned int iostate)
{
	/* Ignore VGA_RSRC_IO and VGA_RSRC_MEM */
	iostate &= VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM;
	switch (iostate) {
	case VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM:
		return "io+mem";
	case VGA_RSRC_LEGACY_IO:
		return "io";
	case VGA_RSRC_LEGACY_MEM:
		return "mem";
	}
	return "none";
}

static int vga_str_to_iostate(char *buf, int str_size, unsigned int *io_state)
{
	/*
	 * In theory, we could hand out locks on IO and MEM separately to
	 * userspace, but this can cause deadlocks.
	 */
	if (strncmp(buf, "none", 4) == 0) {
		*io_state = VGA_RSRC_NONE;
		return 1;
	}

	/* XXX We're not checking the str_size! */
	if (strncmp(buf, "io+mem", 6) == 0)
		goto both;
	else if (strncmp(buf, "io", 2) == 0)
		goto both;
	else if (strncmp(buf, "mem", 3) == 0)
		goto both;
	return 0;
both:
	*io_state = VGA_RSRC_LEGACY_IO | VGA_RSRC_LEGACY_MEM;
	return 1;
}

/* This is only used as a cookie, it should not be dereferenced */
static struct pci_dev *vga_default;

/* Find somebody in our list */
static struct vga_device *vgadev_find(struct pci_dev *pdev)
{
	struct vga_device *vgadev;

	list_for_each_entry(vgadev, &vga_list, list)
		if (pdev == vgadev->pdev)
			return vgadev;
	return NULL;
}

/**
 * vga_default_device - return the default VGA device, for vgacon
 *
 * This can be defined by the platform. The default implementation is
 * rather dumb and will probably only work properly on single VGA card
 * setups and/or x86 platforms.
 *
 * If your VGA default device is not PCI, you'll have to return NULL here.
 * In this case, I assume it will not conflict with any PCI card. If this
 * is not true, I'll have to define two arch hooks for enabling/disabling
 * the VGA default device if that is possible. This may be a problem with
 * real _ISA_ VGA cards, in addition to a PCI one. I don't know at this
 * point how to deal with that card. Can their IOs be disabled at all? If
 * not, then I suppose it's a matter of having the proper arch hook telling
 * us about it, so we basically never allow anybody to succeed a vga_get().
 */
struct pci_dev *vga_default_device(void)
{
	return vga_default;
}
EXPORT_SYMBOL_GPL(vga_default_device);

void vga_set_default_device(struct pci_dev *pdev)
{
	if (vga_default == pdev)
		return;

	pci_dev_put(vga_default);
	vga_default = pci_dev_get(pdev);
}

/**
 * vga_remove_vgacon - deactivate VGA console
 *
 * Unbind and unregister vgacon in case pdev is the default VGA device.
 * Can be called by GPU drivers on initialization to make sure VGA register
 * access done by vgacon will not disturb the device.
 *
 * @pdev: PCI device.
 */
#if !defined(CONFIG_VGA_CONSOLE)
int vga_remove_vgacon(struct pci_dev *pdev)
{
	return 0;
}
#elif !defined(CONFIG_DUMMY_CONSOLE)
int vga_remove_vgacon(struct pci_dev *pdev)
{
	return -ENODEV;
}
#else
int vga_remove_vgacon(struct pci_dev *pdev)
{
	int ret = 0;

	if (pdev != vga_default)
		return 0;
	vgaarb_info(&pdev->dev, "deactivate vga console\n");

	console_lock();
	if (con_is_bound(&vga_con))
		ret = do_take_over_console(&dummy_con, 0,
					   MAX_NR_CONSOLES - 1, 1);
	if (ret == 0) {
		ret = do_unregister_con_driver(&vga_con);

		/* Ignore "already unregistered". */
		if (ret == -ENODEV)
			ret = 0;
	}
	console_unlock();

	return ret;
}
#endif
EXPORT_SYMBOL(vga_remove_vgacon);

/*
 * If we don't ever use VGA arbitration, we should avoid turning off
 * anything anywhere due to old X servers getting confused about the boot
 * device not being VGA.
 */
static void vga_check_first_use(void)
{
	/*
	 * Inform all GPUs in the system that VGA arbitration has occurred
	 * so they can disable resources if possible.
	 */
	if (!vga_arbiter_used) {
		vga_arbiter_used = true;
		vga_arbiter_notify_clients();
	}
}

static struct vga_device *__vga_tryget(struct vga_device *vgadev,
				       unsigned int rsrc)
{
	struct device *dev = &vgadev->pdev->dev;
	unsigned int wants, legacy_wants, match;
	struct vga_device *conflict;
	unsigned int pci_bits;
	u32 flags = 0;

	/*
	 * Account for "normal" resources to lock. If we decode the legacy,
	 * counterpart, we need to request it as well
	 */
	if ((rsrc & VGA_RSRC_NORMAL_IO) &&
	    (vgadev->decodes & VGA_RSRC_LEGACY_IO))
		rsrc |= VGA_RSRC_LEGACY_IO;
	if ((rsrc & VGA_RSRC_NORMAL_MEM) &&
	    (vgadev->decodes & VGA_RSRC_LEGACY_MEM))
		rsrc |= VGA_RSRC_LEGACY_MEM;

	vgaarb_dbg(dev, "%s: %d\n", __func__, rsrc);
	vgaarb_dbg(dev, "%s: owns: %d\n", __func__, vgadev->owns);

	/* Check what resources we need to acquire */
	wants = rsrc & ~vgadev->owns;

	/* We already own everything, just mark locked & bye bye */
	if (wants == 0)
		goto lock_them;

	/*
	 * We don't need to request a legacy resource, we just enable
	 * appropriate decoding and go.